" What use is having a great depth of field, if there is not an adequate depth of feeling?" - W. Eugene Smith
"Cartier-Bresson has said that photography seizes a 'decisive moment', that's true except that it shouldn't be taken too narrowly...does my picture of a cobweb in the rain represent a decisive moment? The exposure time was probably three or four minutes. That's a pretty long moment. I would say the decisive moment in that case was the moment in which I saw this thing and decided I wanted to photograph it." - Paul Strand
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Aperture: Quantity of light
F-stop is a measurement of the size of the lens opening. The larger the f-stop #, the smaller the lens opening which gives you more depth of field. And the smaller the f-stop #, the larger the opening which yields less depth of field.
Shutter: Time of light
Shutter Speed is a measurement of how long the shutter remains open during exposure. Faster speeds will "freeze" motion in your image. (Faster speeds are higher numbers because they are fractions of a second). While slower speeds will "blur" motion.
Digital ISO: Sensitivity of the sensor
ISO Speed is a measurement of how sensitive the image sensor is to light. The "faster" the ISO, which is to say the higher the ISO #, the less exposure it needs. High ISOs are good for low light situations like when shooting indoors. Slower ISO speeds, which are lower ISO numbers, are good for shooting outside and they also produce less "digital noise".
One stop of exposure is either a doubling or a halving of the amount of light!
Law of Reciprocity: E = I x T (Exposure = Intensity x Time)
Doubling I, means we have to half T
1s@f8 = 2s(2x)@f11(.5x)
Exposures are reciprocal – they yield the same density in your image.
f16@1/30 = f11@1/60 = f8@1/125 = f5.6@1/250 = f4@1/500
Depth of Field
When you focus a camera on an object, the distance between the lens and the image sensor is adjusted. In theory, you can only focus on one single distance (the plane of critical focus) and the objects at other distances will be less sharp. But, in most cases, part of the scene will be acceptably sharp both in front of and behind the most sharply focused plane. The further an object is from the plane of focus, the more it will fall out of focus. This region within which objects appear acceptably sharp is called the depth of field.
Depth of Field is controlled by these factors:
1. Aperture size (lens opening):
Larger Aperture (Small f-stop #) = Less Depth of Field (Background more out of focus)
Smaller Aperture (Larger f-stop #) = More Depth of Field (Background more in focus)
2. Focal length of lens:
Longer FL (zoomed in) = Less D of F
Short FL (zoomed out) = More D of F
3. Lens-to-Subject Distance (focus distance):
Close Subject = Less D of F
Far Subject = More D of F
